Advance of technology has made all kinds of electronic devices (such as mouse) smaller. Electronic elements required by those electronic devices also have to be miniaturized. In the electronic devices, switch is the commonly used electronic element to transmit signals.
References for micro switch are seen in numerous prior arts, such as R.O.C. patent Nos. M350087, 507921 and 289485. R.O.C. patent No. M350087 discloses a micro switch including a housing, a common terminal, a normally-closed terminal, a normally-open terminal, a movable contact plate, a tension spring, a pushbutton and a pressing plate. The pressing plate has a dovetail portion to increase the force receiving area of the housing from the pressing plate to avoid the housing from being pierced through. In addition, the tension spring improves control of received force of the movable contact plate to obtain uniform and agile action force, thereby to further enhance performance and reliability of the movable contact plate.
R.O.C. patent No. 507921 also discloses a micro switch including an upper body and a lower body coupled together, a conduction contact and a fixed contact surface on the top of the lower body, an action member with a fixed end anchored on the fixed contact surface and a movable end fastened to a contact element. When a press element is pressed, the bottom thereof is to push the action member. The movable end of the action member is moved accordingly to allow the contact element to contact with the conduction contact to achieve switch function.
R.O.C. patent No. 289485 discloses a micro switch with a detent rib that has a cap with two protrusive rectangular ribs on the surface to control depression movement of the switch to improve durability.
While all the aforesaid prior arts have varying objectives and functions, they have a common feature. Referring to FIG. 1, a micro switch is provided and similar to the micro switches disclosed in the aforesaid prior arts. The micro switch includes a base 30 which has a common terminal 31, a normally-closed terminal 32 and a normally-open terminal 33. The common terminal 31 is coupled with a conductive reed 34. The conductive reed 34 and the normally-open terminal 33 have respectively a first contact portion 341 and a second contact portion 331 corresponding to each other. The conductive reed 34 contacts the normally-closed terminal 32 in normal conditions. When being depressed, the first contact portion 341 presses the second contact portion 331 of the normally-open terminal 33 to form electrical connection between the common terminal 31 and normally-open terminal 33 to output a command or a signal
However, when the conductive reed 34 is pressed, the first contact portion 341 thereof is not moved downwards to contact the second contact portion 331 of the normally-open terminal 33. In fact, the conductive reed 34 has one end connected with the common terminal to function as a fixed end and generates deformation to swing downwards. The second contact portion 331 of the normally-open terminal 33 is formed in a horizontal structure. After the first contact portion 341 swings downwards to generate angle alterations, the first contact portion 341 and the second contact portion 331 are merely connected at a contact point to transmit electric power between the common terminal 31 and normally-open terminal 33. Such operation generates following problems:
1. The area of power transmission is too small, thus results in higher temperature on the contact point between the first contact portion 341 and second contact portion 331.
2. The first contact portion 341 and the second contact portion 331 have greater attraction between them and generate an adhesive phenomenon, thus results in inadequate returning elasticity of the conductive reed 34.
3. To increase the returning elasticity, the elevation of the second contact portion 331 must be higher, thus the distance between the normally-closed terminal 32 and normally-open terminal 33 is shortened. This causes decrease of withstand voltage.
4. The distance that the conductive reed 34 swings downward is relatively short, and the conductive reed 34 also is braced by an edge of the second contact portion 331, hence pressing resistance increases.